Sb2TeO7: A Chiral Antimony Tellurite with Phase-Matchable Second-Harmonic Generation

Noncentrosymmetric (NCS) structures are uncommon among compositionally simple inorganic solids, even when their constituent polyhedra are locally asymmetric. Here, we establish the binary tellurite Sb2TeO7 as a chiral NCS crystal that adopts the orthorhombic space group P212121 (No. 19). Stereochemically active trigonal-pyramidal [TeO3] units bridge two types of distorted Sb-O zigzag chains into a three-dimensional framework, preventing cancellation of the local asymmetric distortions. The structure was obtained through prolonged oxidative solid-state treatment and validated by single-crystal and powder X-ray diffraction. Sb2TeO7 exhibits high thermal stability up to approximately 800 °C and well-balanced nonlinear optical properties. It possesses a wide transparent window from 299 nm to 5.75 μm, a suitable birefringence of 0.106 at 546 nm, and a moderate phase-matchable second-harmonic generation (SHG) response (1.36 × KDP at 1064 nm). Although the SHG response is moderate relative to optimized tellurites, these results demonstrate that an NCS framework and optical anisotropy can be realized in a binary antimony tellurite when the constituent polyhedra assemble cooperatively.